Shoe drum brakes



Deco 8,, 1964 F. T. RIDDY 9 3 SHOE DRUM BRAKES Filed Sept. 24, 1962 5Sheets-Sheet 1 FREDERICK T R/ooy Dec. 8, 1964 F. T. RIDDY 3,160,236

SHOE DRUM BRAKES Filed Sept. 24, 1952 s Sheets-Sheet 2 FREDERICK TFP/DDY F. T. RIDDY SHOE DRUM BRAKES Dec. 8, 1964 5 Sheets-Sheet 3 FiledSept. 24, 1962 Dec 8, 1964 F. T. RIDDY 3,160,236

SHOE DRUM BRAKES Filed Sept. 24, 1962 E3 l v FIG 5 5 Sheets-Sheet 4 F.T. RlDDY SHOE DRUM BRAKES Dec. 8, 1964 5 Sheets$heet 5 Filed Sept. 24,1962 United States Patent 3,169,236 SHUT DRUM BRAKES Frederick ThomasRiddy, Erdington, Birmingham, England, assignor to Sir-ling Limited,Birmingham, England, a British company Filed depto 24, 1962, Ser. No.225,718 Claims priority, application Great Britain, Sept. 22, 1961,33,954/ at 6 Claims. (Cl. 188-795) This invention relates to shoe drumbrakes and in particular to an automatic adjuster for the shoes of abrake of the kind in which arcuate shoes located within a rotatabledrurn are urged apart at one end by an actuator, which may be hydraulicor mechanical or of some other form, and engage at their other endsagainst a stationary abutment or abutments, the actuator and theabutment or abutments being carried by a stationary backplate.

Various proposals have been made for'automatically adjusting theposition of the abutrnents to take up any excessive clearance resultingfrom wear or" the brake linings, and among these proposals have beenarrangements in which movements of the actuator exceeding apredetermined amount cause rotation of a member through a ratchet andpawl mechanism to move the abutments. It is an aim of the invention toprovide an improved arrangement of this kind that is economical tomanufacture and reliable in operation.

According to the invention there is now proposed a shoe drum brake ofthe kind set forth in the opening paragraph above in which an automaticadjusting device comprises a lever engaged at one end by a thrust memberof the actuator that actuates one of the shoes and connected at itsother end to a linkage for adjusting the position of the abutment of atleast that shoe, the lever being pivoted directly or indirectly to thebackplate at an intermediate point in its length.

When the movement of the moving part of the actuator exceeds apredetermined amount it causes sufficient angular movement of the leverto advance the adjusting linkage for the abutment. Preferably it adjuststhe abutments for both shoes simultaneously.

The lever is preferably of arcuate shape, following roughly the web ofthe associated brake shoe, and is pivoted about an axis perpendicular tothe plane of the backplate. Where the actuator has a body that is fixedto the backplate the pivotal axis about which the lever turns can befixed with respect to the backplate but where the actuator is of thefloating type, i.e., its body or in fact all of its parts can move withrespect to the backplate, allowing the actuator to centralise itselfbetween the brake shoes even where the linings on'the two shoes wear atdifferent rates, then according to a further feature of the inventionthe pivotal axis of the lever can be arranged to be linked to movementof the actuator. This can be achieved by mounting that axis on a linkwhich lies close to the lever and is attached at one end to a point nearthe abutment and at the other end to a part of the actuator itself.

The invention will now be further described by way of example withreference to the accompanying drawings, in in which:

FIGURE 1 is an elevation of a part of a backplate with the actuator andabutment and the adjuster of the invention, one of the brake shoes beingindicated in broken line;

FIGURE 2 is a cross-section through the abutment on the line 2-2 inFIGURE 1; 7

FIGURE 3 illustrates a modification of one end of the lever adjuster;

FIGURE 4 is a scrap section on the line 4-4 in FIG- URE 3;

3,l5,235 Fatented Dec. 8, 1964 FIGURE 5 shows a modification in themanner of mounting the lever; and

FIGURE 6 shows a still further modification.

The brake illustrated comprises a backplate 1 carrying two arcuate brakeshoes, of which one is shown in broken lines at 2, the other beingomitted. The lower ends of both shoes engage abutments in a housing 3secured to the backplate while, to apply the brake, the upper ends ofthe shoes are urged apart by an actuator 4. The actuator is notillustrated in detail but it could be mechanical, hydraulic or of anyother form, md it will be suflicient for an understanding of theinvention to know that it is of the floating type and comprises at leasttwo parts which move apart horizontally (as viewed in FIGURE 1) to acton the shoes. Thebody of the actuator 4 centralises itself between theshoes and a thrust member (not shown) engages the end 5 of the web ofthe shoe 2. A similar thrust member (not shown) engages the end of theother shoe.

A lug 6 on the body of the actuator 4 carries a pivot pin 7 and a lug 8on the abutment housing 3 carries a pivot pin 9. Extending between thesepivot pins is an arcuate link iii, which lies close to the brake shoe 2and this link serves as a support for a pin 11 forming the pivotal axisof a lever 12 which is likewise of arcuate shape and lies near the brakeshoe 2. It will be seen that the axis of the pin 11 is perpendicular tothe plane of the backplate 1 and about one third of the way along thelength of the lever 12.. The upper end of the lever 12 forms a thrustpad 13 which is engaged by the same thrustmember of the actuator 4 thatengages the end of the shoe 2.

The lower end of the lever 12 has a pin-and-slot connection at 14 withan arm 15 formed on a ring 16 (FIG- URE 2) in the abutment housing 3.The ring 16 forms a one-way clutch or ratchet device embodied in anadjuster for the abutments of the lower ends of both brake shoes. Theadjuster works on a known principle and comprises a screw 17 with aconed or pyramidal head 18 between a pair of abutments slidable in thehousing 3. One of these abutments is shown at 19 in FIGURE 2 and theother is not shown. A nut 20 in the housing 3 determines the position ofthe screw 17 and hence the separation of the two abutments, and sorotation of the nut 20 in the appropriate direction will move theabutrnents apart to take up excessive clearance between the brakelinings and the drum (not shown). The nut 20 is turned by angularmovement of the ring 16 in this direction and is prevented from rotationin the reverse direction by a further one-way clutch device 21 actingbetween the nut 20 and the housing 3. A screwdriver slot 22 in the screw17 allows the brake to be adjusted initially or after relining of theshoes.

When the brake is correctly adjusted the thrust member of the actuator 4and the lever 12 do not move far enough to cause the nut 20 to turn andadjust the brake. But when the lining of the shoe 2 wears the ring 16 isturned far enough to turn the nut 29, and move the abutments 19 apart.On release of the brake the lever 12 is returned to its originalposition by a spring 23. The movement of the lower end of the lever 12operates the adjuster screw 17 to take up the clearance that hasdeveloped. Preferably the hand of the thread of the screw 17 and thedirection of the clutch ring 1 are such that the adjusting operationoccurs on the release of the brake rather than on its application asthis means that the screw 17 is not working against the brake shoe loadat is turns.

In a modification illustrated in FIGURES 3 and 4 of the arrangementshown, the thrust pad 13 is replaced by a tongue or cranked portion 12aof the end of the lever intervening between the thrust member 13a of theactuator and the end of the brake shoe 2. The return movement of thelever on release of the brake is then efiected 3 y the usual retractingsprings (not shown) of the brake hoes and the spring 23 can be omitted.

Where the brake is of the kind in which the body 4 f the actuator isfixed on'the backplate" the link 10 can e omitted, and the pivot pin 11is then mounted directly n the backplate. This is-illustrated in FIGURE5, which hows an arrangement exactly the same as that of FIG- IRES 1 and2 and the same reference numerals have een used throughout, the onlydilference being that the ivot 11 is mounted directly on the back plateand the ink 16) is omitted together with the lugs 6 and 8 and the ivotpins 7 and 9. The invention is also applicable to rakes of the duo-servotype in which the actuator is lxed to the backplate and the abutmentfloats. This is tlustrated in FIGURE 6, which shows an actuator 411 nda. floating abutment 24 in place of the abutment 3. The lower end of thelever 12!) acts on adjusting means 25 n this floating abutment. In thiscase a link 10a is necssary and as shown this link has a fixed pivot 7awith he actuator 4a and a pivot 9a which is movable with the butment 24.As in the case of lever 12 the lever 12b is ivoted at 11 to the link10a. The spring 23 serves the ientical function asin FIGS. 1 and whichis to act as return spring for the lever 12b. The spring 23 does noterve as a return for the brake shoe inasmuch as these re returned byconventional retracting springs not shown ii any of the drawings.

I claim:

1. A brake comprising a back plate, a drum mounted or rotation about anaxis perpendicular to the planetof aid back plate, an arcuatefriction-surfaced brake shoe, aid brake shoe being mounted on said backplate within aid drum and and adapted to frictionally engage the nnersurface of said drum, an actuator body, shoe- .ctuating means housedwithin said body and engaging first end of said shoe, abutment meansengaging a econd end of said shoe, said actuator body being capable flimited circumferential movement with respect to said ack plate, anadjustable connection between said abutnent means and said second end ofthe shoe, an arcuate ink extending substantially alongside said shoe,and aivotally connected at its two ends respectively to said ,ctuatorbody and said abutment means, an arcuate lever xtending substantiallyalongside said link and shoe, one nd of said lever being engaged by saidshoe actuating means and the other end of said lever being operativelypplied to said adjustable connection, and a pivotal con- ;ection betweensaid link and said lever about an axis ntermedi-ate the length of eachand perpendicular to he plane of said back plate.

2. A brake comprising a back plate, a drum mounted or rotation about anaxis perpendicular to the plane of aid back plate, an \arcuatefriction-surfaced brake shoe, aid brake shoe being mounted on said backplate with said drum and adapted to frictionally engage the rmer surfaceof said drum, an actuator body fixedly counted on said back plate, shoeactuating means housed vithin said body and engaging a first end of saidshoe, butment means engaging a second end of said shoe, said butmentmeans being capable of limited circumferential movement with respect tosaid back plate, an adjustable onnection between said abutment means andsaid secnd end of the shoe, an arcuate link extending substaniallyalongside said shoe and pivotally connected at its wo ends respectivelyto said actuator body and said butment means, an arcuate lever extendingsubstanially alongside said link and shoe, one end of said lever eingengaged by said actuating means and the other rid of said lever beingoperatively applied to said adlstable connection, and a pivotalconnection between aid link and said lever about an axis intermediatethe :ngth of each and perpendicular to the plane of said ack plate.

3. A brake comprising a back plate, a drum mounted J1 rotation withrespect to said back plate about an axis perpendicular thereto, anarcuate friction-surfaced brake shoe, said brake shoe beingmountedwithin said drum for limited movement with respect to said back and saidbrake shoe being adapted to frictionally engage the inner surface ofsaid drum, an actuator body, shoe-actuating means supported on saidbody, an operative connection between said shoe-actuating means and afirst end of said shoe, abutment means, adjustable connecting meansbetween said abutment means and a second end of said shoe, an arcuatelever, said lever extending substantially concurrently with said shoe,one end of said lever lying adjacent said first end of said shoe andbeing caused to a move therewith, an arcuate link extendingsubstantially concurrently with said shoe and lever, a connectionbetween one end of said link and said actuator body, a connectionbetween the other end of said link and said abutment means, a pivotalconnection between said lever and said link at a point intermediate thelength of each about an axis perpendicular to said back plate, and anoperative connection between said adjustable connecting means and theother end of said lever.

4. A brake comprising a back plate, a drum mounted for rotation about anaxis perpendicular to the plane of said back plate, an arcuate frictionsurfaced brake shoe mounted within said drum and adapted to frictionallyengage the inner surface thereof, a shoe actuating member engaging oneend of said shoe for applying the brake upon operation of said shoeactuating member, an abutment member engaging the second end of saidshoe, one of said members being capable of limited circumferentialmovement with respect to said back plate, an adjustable connectionbetween said abutment member and the second end of said shoe, an arcuatelink extending substantially alongside said shoe and pivotally connectedat its two ends respectively to said actuating member and to saidabutment member, an arcuate lever extending substantially alongside saidlink and shoe, one end of said lever being engaged by said actuatingmember and the other end of said lever being operatively connected tosaid adjustable connection, and a pivotal connection between said linkand said lever about an axis intermediate the length of each andperpendicular to the plane of said back plate.

5'. A brake comprising a back plate, a drum mounted for rotation withrespect to said back plate about an axis perpendicular thereto, anarcuate friction-surfaced brake shoe, said brake shoe being mountedwithin said drum for limited movement with respect to said back plateand said brake shoe being adapted to frictionally engage the innersurface of said drum, an actuator body supporting actuating means, saidbody being capable of a limited circumferential movement relative to thebackplate, an operative connection between said shoe-actuating means anda first end of said shoe, an abutment housing fixedly mounted on thebackplate, said housing supporting abutment means, adjustable connectingmeans between said abutment means and a second end of said shoe, anarcuate lever, said lever extending substantially concurrently with saidshoe, one end of said lever lying adjacent said first end of said shoeand being caused to move therewith, an

arcuate link extending substantially concurrently with.

said shoe and lever, a connection between one end of said link and saidbody, a connection between the other end of said link and said housing,a pivotal connection between said lever and said link at a pointintermediate the length of each about an axis perpendicular to said backplate, and an operative connection between said adjustable connectingmeans and the other end of said lever.

6. The brake of claim 4 wherein said shoe actuating member comprises abody part and an actuator part cooperating with said body part andmovable with respect thereto in engagement with one end of said shoe forapplying the brake, said abutment member comprising a second body partand an abutment supported by said body part and engaging the second endof said shoe,

5 6 said adjustable connection including adjuster means co- 2,762,4639/56 Brooks 18879.5 operating with said second body pan: and saidabutment 3,034,602 5/62 Bauman 188-79.5 for moving said abutmentrelative to said second body 3,074,514 1/63 Mossey et a1 188-795 Pan 5FOREIGN PATENTS References Cited by the Examiner UNITED STATES PATENTS612,360 11/48 Great Britain. 1,810,628 6/31 Stevens. ARTHUR L. LA POINT,Primary Examiner.

1,824,552 9/31 Khezarjian 188-795 10 2,132,576 10/38 Nachtwey 188-795GRAHAM cRAVEREmmme

1. A BRAKE COMPRISING A BACK PLATE, A DRUM MOUNTED FOR ROTATION ABOUT ANAXIS PERPENDICULAR TO THE PLANE OF SAID BACK PLATE, AN ARCUATEFRICTION-SURFACED BRAKE SHOE, SAID BRAKE SHOE BEING MOUNTED ON SAID BACKPLATE WITHIN SAID DRUM AND AND ADAPTED TO FRICTIONALLY ENGAGE THE INNERSURFACE OF SAID DRUM, AND ACTUATOR BODY, SHOEACTUATING MEANS HOUSEDWITHIN SAID BODY AND ENGAGING A FIRST END OF SAID SHOE, ABUTMENT MEANSENGAGING A SECOND END OF SAID SHOE, SAID ACTUATOR BODY BEING CAPABLE OFLIMITED CIRCUMFERENTIAL MOVEMENT WITH RESPECT TO SAID BACK PLATE, ANADJUSTABLE CONNECTION BETWEEN SAID ABUTMENT MEANS AND SAID SECOND END OFTHE SHOE, AN ARCUATE LINK EXTENDING SUBSTANTIALLY ALONGSIDE SAID SHOE,AND PIVOTALLY CONNECTED AT ITS TWO ENDS RESPECTIVELY TO SAID ACTUATORBODY AND SAID ABUTMENT MEANS, AN ARCUATE LEVER EXTENDING SUBSTANTIALLYALONGSIDE SAID LINK AND SHOE, ONE END OF SAID LEVER BEING ENGAGED BYSAID SHOE ACTUATING MEANS AND THE OTHER END OF SAID LEVER BEINGOPERATIVELY APPLIED TO SAID ADJUSTABLE CONNECTION, AND A PIVOTALCONNECTION BETWEEN SAID LINK AND SAID LEVER ABOUT AN AXIS INTERMEDIATETHE LENGTH OF EACH AND PERPENDICULAR TO THE PLANE OF SAID BACK PLATE.